The present invention relates to a frictionless hydraulic damper and to a frictionless hydraulic damper which can also function as a snubber.
By way of background, frictionless hydraulic dampers are desired for certain applications to attenuate forces between relatively movable objects where the internal frictional resistance of the dampers is objectionable. There are certain hydraulic devices which function solely as dampers, and there are other hydraulic devices which function as dampers when they are subjected to forces at low velocities and also function as snubbers when they are subjected to forces at high velocities. By way of definition, a hydraulic snubber must always function as a damper when placed between relatively moving external members which move relative to each other below a predetermined velocity, and it functions as a snubber when the external members move relative to each other above the predetermined velocity.
By way of further background, and by way of specific example, in nuclear plants small pipes are suspended by hangers in the nature of snubbers which are subjected to forces within the 200 to 3,000 pound range. In the past it has been highly impractical to use hydraulic snubbers for this application for two reasons. Firstly, radiation affected the plastic or rubber seals and thus permitted them to leak. Secondly, seals create friction and where small pipes were suspended by snubbers which were subjected to forces between 200 and 500 pounds, the seal friction was a substantial portion of the applied forces which did not allow the small pipe to move in an unrestrained manner while being supported. Therefore, in the past hydraulic snubbers were not used for the foregoing applications, and instead highly complex mechanical snubbers were used. These required high maintenance and many times were unreliable because of their complexity.